Warp tensioning devices for looms



Aug. 27, 1963 T. HINDLE 3,101,747

WARP TENSIONING DEVICES FOR LOOMS Filed Feb. 2l 1961 3 Sheets-Sheet l Aug. 27, 1963 T, H'INDLE 3,101,747

WARP TENSIONING DEVICES FOR LOOMS Filed Feb. 21, 1961 5 Sheets-Sheet 2 INVE NTOR:

Aug 27, 1963 T. HINDLE 3,101,747

WARP 'TENsIoNING DEVICES FOR LooMs Filed Feb. 2l, 1961 3 Sheets-Sheet 3 United States Patent 3,l01,747 WARP TENSlUNlNG DEVCES FOR LOMS Thomas Hindle, Thornlea, Beardwood Brow,

Blackburn, Lancashire, England Filed Feb. 2l, 1961, Ser. No'. 90,800

Claims priority application Great Britain Feb'. 25, 1960 l v Ciaims. (Cl. 139-109) With such devices, the baskY rest is weighted by weights, springs or other means, so as to apply a constant force pulling it away from the loom healds and into the bight of the warp threads, which, in turn, are fed from the beam by a positive let-off motion arranged to rotate the beam. In action, as weaving progresses, the back rest or whip roll is drawn towards the 'loom healds by the take-up of the loom, and the let-ofi motion is inactive until the back rest has been thus advanced towards the loom healds beyonda predetermined position whereupon the let-off motion is activated and brought into operation until the back rest or whip roll has moved back to another predetermined position when the let-oi mot-ion is de-activated, such movement is stopped and the cycle of operation above described starts again.

It is always the aim of a Warp tensioning device to maintain Ia constant tension onthe warp threads and var- `ious mechanisms are known which attempt to achieve There are, however, several factors which are respon-v sible for variations of 'warp tension, -but one factor, which does not appear at present to have received consideration, is the change of angularity of the run of the warp threads which extend between the back rest or whip roll and the warp beam. This change of angnlarity derives both from change of position of the back rest or whip roll in its movements Ito-and-fro between its predetermined advanced and retraced positions as aforesaid, and commonly from change of diameter of the warp beam as let-oit progresses as between a full beam and one which is due for replacement. Thus, when the bight angle becomes obtuse, a lesser force on the back rest is required than when such angle is acute to provide the same tension, and therefore, `also to maintain a constant warp tension.

Another `factor which is responsible for. variation of warp tension is the physical weight of the sensitive backrest or whip roll, especially when this is mounted in the usual 4manner on pivoted opstanding arms. Such weight, by reason of the change of angularity of such arms with ICC of leverage proportional tov the change of angularity of the warp threads passing up to the back rest and thereby to apply to the back rest a force so varying with such angnlarity of the warp threads as to result in a substantially constant warp tension.

The warp` tensioning device aforesaid may be further characterised'in that the compensating lever mechanism is so constructed as to employ a component of force derivedfrom the back rest as a function of the angularity of the run of the lwarp threads passing up to fthe back rest.

In the accompanying drawings: FIG. 1 is a diagram showing the basic principle of forces operating onthe movable back restorlwhipI roll of a warp tensioning device of the kind referred to;

FIG. 2 is a fragmentary vertical section through the axis of the whip roll illustrating one desirablefand'practical embodiment of the invention, the whipA roll being shown in its normal position;

FIG. t3 is a view similar to FIG. 2, but showin-g the whip roll as having moved to the left of its normal position in response to increase in tension of the warp yarns;

FlG. 4 is a View similar to FIG. 2, but showing the whip roll as having moved to the right of its normal position; and

`FIG. 5 is a fragmentary elevation, showing the whip roll and the multiple compensating lever as viewed `from the rear 'end of the loom. y

As shown in FIG. 1, the warp threads a from a warp beam b pass over a :back rest or whip roll c 'which is movable between dotted extreme positions shown at c1 and c2. A weight W on the end of a cranked lever-d, .pivotedat e, appliesa force P to the back rest which force is substantially constant for the small changes of angle of the lever d normally obtaining. The positions c1 and c2 are exaggerated only to show a visible change n f and direction.the tension T is not equal to P when the change of position of the back rest gives a varying com- ,l

- sion.

According to the invention, a war-p tensioning rdevice of the kindreferred to is characterised by compensating lever means between an applied constant force and the back rest so constructed as to have a change of angularity back rest is displaced from such position. ln fact, when displaced to the position c1, the tension T is equal to P plus a component which is a function of the change of angularity, whilst at the position c2 the tension T is equal to P minus such a component.

In the embodiment of the present invention illustrated in FIGS. 2, 3 and 4, and wherein the warp beam is shown at 4, and the whip roll or back rest at 2, a iixed yarn guide 3 (here shown as a round rod) is so arranged, relatively to the warp beam and whip roll that, in passing from the warp beam to the Whip roll,.a warp yarn forms a bight about the ixed guide 3, the run a2 of yarn,

`approaching -the xed guide 3, making an angle with a run by a lever assembly comprising a plurality of like supports 5 (four being shown in FIG. 5, by way of example), thevlength of the tube .2a being at least as great as the width of the sheet W of warp yarns. Each of these supports S comprises a ring-like portion which tightly embraces and is fixed to the tube 2a. Each support also has la downwardly projecting lug 5b at lits lower portion,

in which an anti-friction roll '6 isv journaled. The rolls 6 rest upon a fixed horizontal guide 7, which may be a part of the loom frame, thus vprow'ding for bodily motion of the whip roll or backrest from frontlto rear of the loom. Each support S also comprises an integral elongate, normally horizontal arm 5a projecting rearwardly from the upper part of its ring-like portion and having, at its free or rear end an opening whose center (when the parts occupy the normal position illustrated in FIG. 2) is in the plane of the warp sheet W formed by the yarns a.

The tube 2a rigidly unites the spaced supports 5, and the several supports, including their arms 5a, the lugs Sb, and the rolls 6 are here for convenience referred to as the 'whip roll lever assembly or merely as the lever assembly and this assembly may rock about the points of contact of the rolls `t5 with the guide 7, said points of contact defining a fulcrum axis about which the lever assembly may, rock.

A'lever 9 is associated -with each of the supports 5, each lever being pivotally connected to the arm. 5a of the corresponding support by a pivot pin 8 passing through the yaforesaid aperture in the free end of the arm 5a of the support. Each of the levers 9 is pivotally supported by a corresponding stand or bracket B (FIG. 5) mounted on the loom frame, each bracket having a pivot element l on which the lever 9 is mounted, with its axis parallel to that of the warp beam. As shown in FIG. 2, the axes of the pivot elements `10 are below the horizontal plane of the axis of the Whip roll 2. In the following discussion, the levers 9 are collectively referred to as the compensating lever, their connection to the whip roll lever assembly constraining all of the several independent levers 9 lto act as a unit. `One at least of the levers -9 (and preferably each of them) has a rigid downwardly directed extension 9a.

To the lower end of each of the lever arms 9a ther-e is attached, by means of a pivot pin 11, the rear end of a .connecting rod 12 whose forward end (FIG. 2) is pivotally secured at 11a (as shown in dotted lines) to the vertical arm of a bell crank lever 13 pivotally secured at 13a to a part of `the loom frame and Whose horizontal arm i311 carries a weight 14. With the parts positioned as shown in PIG. 2, the fulcrum axis, defined by the points of contact of the rollers 6 with the horizontal support '7, is vertically below the axis of the tube 2a. *In the practical embodiment of the invention, the parts may be so designed that a single weight 14 will suflice to apply apconstant force to all of the levers 9, tending to rock their lower ends forwardly, thus providing a force which tensions the warps forming the sheet W.

The position of the whip roll 2, shown in FIG. 2, wherein the axis of the roll is vertically above the fulcrum axis (where the roll 6 contacts the support 7), and wherein the lever 9 is vertical, is herein referred to as the normal position of the parts, since, in this position, the turning moment about the fulcrurn axis has no effect upon the lever 9 since the vertical component of said turning moment is normal to the shaft 10.

The aforesaid relative positions, shown in FIG. 2, arev substantially maintained for all positions of the back rest within the permitted angle of movement of the levers 9. Tensioning force for the warp a to provide the pull T is applied to the end of each lever member by the lever 9, pivotally mounted at its pivot 10, such pivot being stationary. In this normal position of the parts, as shown in FIG. 2, the vertical component of force at the pivot 8, resulting fromthe tension of the vertical run a1 of the said warp threads has, therefore, no turning moment about the pivot 10 and the tension T in the warp threads between the back rest and .the loom healds will be equal to the force P obtained Efrom the weight 14. The proportional dimensions here shown are such that X=2x and It the whip roll 2 move to the right or left from the positionillustrated in FIG. 2, then the turning moment about the fulcrum axis 6 has a component acting in the horizontal direction Iabout the pivot lill. However, such motion of the whip roll, to theright or left, concomitantly varies the slope of the runa1 of yarn extending from the xed guide 3 to the whip roll, thus developing a horizontal component of the reaction force acting upon the whip roll, such that when the whip roll moves to the right of the position shown in FIG. 2, the reaction force on the whip roll, which opposes the force P, is increased whereas when fthe Whip roll moves to the left of the position shown in FIG. 2, the reaction force opposing the force P is decreased, so that, in either event, there is a change in fthe tension T on the warp yarns extending from the whip roll to the cloth beam.

However, by the provision of the compensating lever, such variation in the force P, resulta-nt from motion of the whip roll, is prevented since the downward component of force at 8 of the reaction force on the whip roll provides an additive or subtractive turning moment about the fulcrum axis of the compensating lever 9.

As shown, however, in FIG. 3, as the back rest or Whip roll 2 is drawn to the position corresponding to the posirtion c1 of FIG. l, the vertical component of force at 8, resolved about the pivot 10, exerts -a :turning moment in an anti-clockwise direction, which is a function of the langle 20 of the lever from the vertical and which, in turn, is a function of the angle 0 `from the vertical of the run a1 of the warp threads. This results from the proportions shown in FIG. 2 in which the length y of the lever between the pivots at 8 and 10 is half the length Y of the inclined run of the warp threads and the vertical component of force at 8 will be half `the vertical component from such inclined run of the warp threads. Consequently, assuming the beam is held from rotation, the tension T in the position shown in FIG. 3 will remain constant because the horizontal component of force at the pivot 8 is equal to the force P applied by the weight less the turning moment of the vertical force component at the pivot S around the pivot 10, which deduction compensates for the horizontal force component due to the inclination through rthe angle 0 of the hitherto vertical portion of the warp passing up from the guide bar to the back rest, by positioning the pivot llll at a horizontal distance X equal to twice the radius x of the back rest.

Similarly, as is obvious from FIG. 4, the tension T will remain constant in spite of inclination of the vertical portion of the warp threads in lthe other direction because the sum of the horizontal forces at the pivot 8 will be equal to the force P derived from the weight 14, plus the horizontal component fof force derived from the clockwise force couple about the fulcrum 6 from the vertical force component at the pivot 8 cancelling the equal horizontal component from the inclinati-on of the previously vertical portion of the warp. In short, compensation is obtained when the proportions are such that il y In the example given, both these ratios are 2:1, but any other convenient ratio may be used. The above theory, of course, is of a substantial nature, that is to say, for rthe small angularities normally involved, the ratios are substantially of the order specified.

Thus, the warp tensioning device above described employs a change of angularity of the levers 9 so proportioned to the change of angularity of the inclined portion of the Warp threads as to result in a substantially constant Warp tension, and in so doing, it employs a component of force derived directly from the angularity of the levers las a function of the angularity of the inclined warp threads. The principle applies obviously to intermediate positions within normal requirements for movement of the back rest.

The invention is obviously not limited to the constructional details of the example above described which may be varied to employ the same principles of operation of leverage varying as a function of warp inclinations.

I claim:

1. In combination, in a weaving loom of the kind which comprises Va warp beam, warp let-oil devices, a whip roll whose axis is parallel to that of the warp beam and which is bodily movable in a front-to-rear direction in response to variations in Warp tension, and thereby controls the operation of the let-off, and means for applying tension to the warps extending from the 'whip roll to they healds of the loom, characterized in having a fixed yarn guide which the yarns contact on their way from the warp beam to Ithe whip roll, said xed yarn guide being so located relatively to the warp beam and whip roll that the angle between the runs of yarn in approaching and leaving the yarn guide is always less than 180 regardless fof the diamextending from the iixed guide tto the whip roll is vertical regardless of the diameter of the yarn mass on the warp beam.

3. A warp tensioning device of that kind wherein 'a movable whip roll is located in a bight of the warp yarns leading from the warp beam to the :loom healds and wherein variations in the position of the whip roll in response to varying warp tension controls let-oli means for the war-p, characterized in h-aving a lixed guide over which the Warp yarns pass on their way from the warp beam to the whip roll and which is so positioned that, in the normal position of the whip roll, the run of warp yarns extending between the iixed guide and the Whip roll is substantially vertical, Xa lever assembly which supports the whip roll to rock about lan `axis below and parallel to the axis of whip roll proper, said lever assembly having a rigid, rearwardly extending arm, a compensating lever pivoted to rock about `an axis parallel to that of the whip roll Vand whose lfree end is normally in the plane of the warp `sheet extending forwardly from the whip roll, a pivot element connecting the `free end of the compensating lever to the rearwardly extending arm of the whip roll lever assembly, anda weight and connections between the weight and the compensating lever operative to maintain the warp yar-ns under tension, the relative proportions of the parts `when the whip: roll is in normal position being expressed by the-equation E X w y where -X represents the distance `from the pivot element which connects the compensating lever to the whip roll assembly lever and the vertical plane through the axis of the whip roll; x equals the radius of the yarn-contacting surface of the whip roll; Y equals the length of the run of the Warp yarn extending from the guide bar to the whip roll; and y equals the length of the compensating lever between its fulcrum and Athe point `at which it is pivotally connected to the Whip roll lever assembly.

4. Warp tensioning means according to claim 3, further ,characterized in that the relative arrangement :and dimensions of the parts are such that, when motion of the whip roll from its normal position, in response to increased warp tension, causes the run of warp extending from the guide lbar to the whip roll to deviate from the vertical by an angle of H, the compensating lever will be concomitantly rocked so that it willy incline in the same direction as said run of warp, but will make an angle with the vertical of 20.

5. In combination, in a weaving loom of the kind which comprises a warp lbeam, warp let-off devices, a whip roll whose Iaxis is parallel to that of the Warp beam and which is bodily movable in a front-to-rear direction in accordance with varying warp tension, and by such bodily movement controls the operation of lthe let-oit,

yand means for applying tension to the warp yarns extending from the whiproll to the healds of the loom, characten'zed in having a lixed yarn guide whose yarn-contacting surface is parallel to the axis of the warp beam and which is so located, relatively to the warp beam and whip roll that, in the normal position of the whip roll, the warp yarns extend vertically up from said yarn guide to the whip roll, and means operative automatically to maintain the tension of the warp yarns between the whip roll and cloth beam substantially constant regardless of variations `in the slope ofthe warp yarns extending from said yarn gui-de to the whip roll occasioned by bodily motion of the whip roll from normal position.

6. The combination according to claim 5, wherein the means for maintaining uniform tension upon ia warp yam comprises a lever assembly lfor supporting the whip roll, said assembly having its fulcrum parallel to, but spaced fro-m and below that of the whip rol-l, the means vfor applying tensioning force to the warp yarns comprising a vcompensating lever which is normally vertical yand whose 'free end is normal-ly disposed in the horizontal plane of the warp yarns leading from the whip roll to the healds of the loom, means whereby a substantially constant force is applied to said compensating lever tending to rock the latter in a direction such ias to `apply tension to the yarn extending fromy the whip roll to the loom healds,l and means connecting the lever assembly which supports the whip roll to the -free end of said compensating lever whereby, as the whip roll moves bodily `from normal position, said compensating lever is concomitantly rocked from vertical position.

7. The combination according to claim 5, wherein the length of the compensating lever is to the length of the warp yarn extending from the yarn guide to the whip roll as the angle of slope of the warp yarns extending from the yarn guide to the whip roll, resultant from motion of the whip roll from normal position, is tothe angle 'of slope of the compensating lever. v and said of them and int hat the and of the and that the 8. The combination according to claim 5, wherein the means for maintaining unifonm tension upon the warp yarn :comprises a lever assembly which supports the whip roll, said assembly having coaxial rollers which rest npon and may roll along a horizontal guide and whose contact 'with said `guilde defines a fulcrum axis, the whip roll being thereby supported for bodily movement and also for rocking motion about the 'iulcrum axis of the lever assembly,

y a compensating lever which is pivoted to rock about a stixed axis parallel to said fulcrum axis of the lever assembly, and pivot means connecting the free end of said compensating lever to the lever assembly at a point spaced from the yfulcrum axis of the latter, the tensioning force being so applied to said compensating lever as to tend to rock the latter in a direction to tension the yarn extending from the whip roll to the loom healds.

9. 'Ilhe combination according to rcllairn 5, further characterized in that the means for maintaining nnifonm tension upon the 4warp yarns comprises a lever assembly provided with coaxial rollers which rest upon a xed horizontal guide and whose point of contact with the guide defines a fulcrum axis for the lever assembly, a compensating lever arranged to rock about an axis parallel to the yfulcrum axis of the lever assembly and spaced from the latter -a distance exceeding the radius of the whip roll, said lever assembly having a rigid, elongate, normally, substantially horizontal arm, pivot means connecting sai'd rigid, elongate arm to the free end of the compensating lever, the latter comprising a nigid downwardly ydirected extension to which the tensioning vforce is applied, the lever assembly which supports the whip roll comprising means for so suppontin-g the whip roll that the axis of the latter is panallel to the ulcrum axis or the assembly and between said fulcrum axis and that part of fthe lever assembly `from which the elongate arm extends.

l0. The combination according to claim 5, wherein the @parts arev so dimensioned and v'arranged' that, when the 1 Whip roll'is'in normal position, the axis of the Whip roll is above the yfulcriunaxis''of the lever assembly, the surface of the ixedguidefrorn which the warp yarns extend to the` Whip roll is vertically below the end of la horizontal radius ofthe Whip roll, the length of the'compensating lever,

' between its pivot point and its connection to the lever assembly which supportshe Whip roll is spaced from the f vertical plane of the fulcrumabout which'the Whip roll rocks a distance equal to twice the radius of the Whip roll. References Cited1 inlthe file of. this patent UNITED' STilTESk PATENTS Davis Jan. 27, 1931 2,420,957 Lakeland May 20, 1947 2,775,415 Rush s Dec.' 25, 1956 FOREIGN PATENTS 613,525 France Aug. 27, 1926 

1. IN COMBINATION, IN A WEAVING LOOM OF THE KIND WHICH COMPRISES A WARP BEAM, WARP "LET-OFF" DEVICES, A WHIP ROLL WHOSE AXIS IS PARALLEL TO THAT OF THE WARP BEAM AND WHICH IS BODILY MOVABLE IN A FRONT-TO-REAR DIRECTION IN RESPONSE TO VARIATIONS IN WARP TENSION, AND THEREBY CONTROLS THE OPERATION OF THE "LET-OFF" AND MEANS FOR APPLYING TENSION TO THE WARPS EXTENDING FROM THE WHIP ROLL TO THE HEALDS OF THE LOOM, CHARACTERIZED IN HAVING A FIXED YARN GUIDE WHICH THE YARNS CONTACT ON THEIR WAY FROM THE WARP BEAM TO THE WHIP ROLL, SAID FIXED YARN GUIDE BEING SO LOCATED RELATIVELY TO THE WARP BEAM AND WHIP ROLL THAT THE ANGLE BETWEEN THE RUNS OF YARN IN APPROACHING AND LEAVING THE YARN GUIDE IS ALWAYS LESS THAN 180* REGARDLESS OF THE DIAMETER OF THE YARN MASS ON THE WARP BEAM. 